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We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on various time scales and present a new sea-level record for the past 100 million years (My). Long-term sea level peaked at 100 ± 50 meters during the Cretaceous, implying that ocean-crust production rates were much lower than previously inferred. Sea level mirrors oxygen isotope variations, reflecting ice-volume change on the 104- to 106-year scale, but a link between oxygen isotope and sea level on the 107-year scale must be due to temperature changes that we attribute to tectonically controlled carbon dioxide variations. Sea-level change has influenced phytoplankton evolution, ocean chemistry, and the loci of carbonate, organic carbon, and siliciclastic sediment burial. Over the past 100 My, sea-level changes reflect global climate evolution from a time of ephemeral Antarctic ice sheets (100 to 33 Ma), through a time of large ice sheets primarily in Antarctica (33 to 2.5 Ma), to a world with large Antarctic and large, variable Northern Hemisphere ice sheets (2.5 Ma to the present).
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The Phanerozoic Record of Global
Sea-Level Change
Kenneth G. Miller,
Michelle A. Kominz,
James V. Browning,
James D. Wright,
Gregory S. Mountain,
Miriam E. Katz,
Peter J. Sugarman,
Benjamin S. Cramer,
Nicholas Christie-Blick,
Stephen F. Pekar
We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on
various time scales and present a new sea-level record for the past 100 million years
(My). Long-term sea level peaked at 100 T 50 meters during the Cretaceous, implying
that ocean-crust production rates were much lower than previously inferred. Sea level
mirrors oxygen isotope variations, reflecting ice-volume change on the 10
scale, but a link between oxygen isotope and sea level on the 10
-year scale must be
due to temperature changes that we attribute to tectonically controlled carbon dioxide
variations. Sea-level change has influenced phytoplankton evolution, ocean chemistry,
and the loci of carbonate, organic carbon, and siliciclastic sediment burial. Over the past
100 My, sea-level changes reflect global climate evolution from a time of ephemeral
Antarctic ice sheets (100 to 33 Ma), through a time of large ice sheets primarily in
Antarctica (33 to 2.5 Ma), to a world with large Antarctic and large, variable Northern
Hemisphere ice sheets (2.5 Ma to the present).
luctuations in global sea level (eustasy)
result from changes in the volume of
water in the ocean or the volume of
ocean basins (Fig. 1) (1–4). Water-volume
changes are dominated by growth and decay of
continental ice sheets, producing high-
amplitude, rapid eustatic changes Eup to 200
m and 20 m per thousand years (ky)^. Other
processes that affect water volume occur at
high rates (10 m/ky) and low amplitudes (È5
to 10 m): desiccation and inundation of mar-
ginal seas, thermal expansion and contraction
of seawater, and variations in groundwater and
lake storage. Changes in ocean basin volume
are dominated by slow variations in sea-floor
spreading rates or ocean ridge lengths (100 to
300 m amplitude, rates of 10 m/My). Variations
in sedimentation cause moderate amplitude
(60 m), slow changes (10 m/My). Emplace-
ment of oceanic plateaus produces moderate-
ly rapid rises (60 m/My) but slow falls due to
thermal subsidence (10 m/My).
Eustatic variations can be estimated from
satellite measurements, tide gauges, shoreline
markers, reefs and atolls, oxygen isotopes
O), and the flooding history of continental
margins and cratons. Satellite measurements
are limited to the past 10 years (5), whereas
tide gauge records extend back only È150
years (3). The most recent pre-anthropogenic
sea-level rise began at about 18 ka and can be
measured by directly dating shoreline markers
(fig. S1). Tropical reefs and atolls (fig. S2)
provide the most reliable geological estimates
by dating Bfossil sunshine[ (e.g., shallow-
dwelling corals) and have provided a precise
estimate for the last sea-level lowstand (120 T
5 m below present at 18 ka) (fig. S2) (6, 7).
However, most coral records are from regions
with complicated uplift/subsidence histories,
are difficult to recover and date (particularly
beyond a few 100 ky), and have poorly pre-
served lowstand deposits.
The growth and decay of continental ice
sheets causes eustatic changes that are in-
directly recorded in the chemistry of forami-
nifera because ice has lower d
O values than
seawater (fig. S2) Ee.g., (8, 9)^. Oxygen isotope
values provide a proxy for glacioeustasy, but
O-based reconstructions are subject to
several uncertainties: (i) Calcite d
also vary as a function of temperature. (ii)
Surface-ocean d
O values are influenced by
local evaporation-precipitation effects on
seawater. (iii) Postdepositional alteration (dia-
genesis) may overprint original d
limiting useful records to sediments younger
than 100 My.
Continents have been flooded many times
in the geologic past (Fig. 2). However, the
flooding record is not a direct measure of
eustatic change because variations in sub-
sidence and sediment supply also influence
shoreline location. Regional unconformities
(surfaces of erosion and nondeposition) divide
the stratigraphic record into sequences and
provide a key to eustatic change. Unconform-
ities result from sea-level fall or tectonic uplift
(10–12). Similar ages of sequence boundaries
on different continents have been interpreted
as indicating that the surfaces were caused by a
global process, eustasy Ee.g. (10, 11)^. The link-
age with d
O increases for the past 40 My
(13) indicates that most sequence boundaries
resulted from eustatic falls driven by the
growth of continental ice sheets.
Although unconformities poten-
tially provide the timing of eustatic
lowstands, extracting global sea-
level history from the stratigraphic
record requires a quantitative method
that distinguishes the contributions
of eustasy, subsidence, and sedi-
ment accumulation. Backstripping
is an inverse technique that can be
used to quantitatively extract sea-
level change amplitudes from the
stratigraphic record. It accounts for
the effects of sediment compac-
tion, loading (the response of crust
to overlying sediment mass), and
water-depth variations on basin sub-
sidence (14). Tectonic subsidence at
a passive margin is modeled with
thermal decay curves and removed
Department of Geological Sciences, Rutgers University,
Piscataway, NJ 08854, USA.
Department of Geo-
sciences, Western Michigan University, Kalamazoo, MI
49008–5150, USA.
Lamont-Doherty Earth Observa-
tory of Columbia University, Palisades, NY 10964, USA.
New Jersey Geological Survey, Post Office Box 427,
Trenton, NJ 08625, USA.
Department of Geological
Sciences, University of Oregon, Eugene, OR 97403–
1272, USA.
School of Earth and Environmental
Sciences, Queens College, 65-30 Kissena Boulevard,
*To whom correspondence should be addressed:
Fig. 1. Timing and amplitudes of geologic mechanisms of
eustatic change derived from (1–4). SF, sea floor; Cont,
continental. SCIENCE VOL 310 25 NOVEMBER 2005
to obtain a quantified eustatic estimate in the
absence of local tectonic complexities.
We review the record of and uncertainties
in eustatic changes over the past 543 My on
three time scales: (i) a long-term trend (10
years) that has been attributed largely to
variations in sea-floor spreading; (ii) the 10
year scale that is among the most prominent
features of the stratigraphic record; and (iii) the
-year scale that is dominated by
changes in ice volume and controlled by astro-
nomical variations in insolation. We present a
new eustatic record for the past 100 My, with
implications for causal mechanisms for both
- and 10
-year changes.
Long-Term Flooding of Continents
Sloss (15) recognized that North America
experienced five major Phanerozoic floodings
(Fig. 2) and attributed these changes to sub-
sidence and uplift of the craton. Vail and col-
leagues at Exxon Production Research Company
(EPR) recognized similar 10
-year scale
‘supersequences’ that they attributed to global
sea-level changes (10, 11, 16). Others have re-
constructed continental flooding history on the
-year scale (4, 17–19) (Fig. 2) and
inferred eustatic changes from commonalities
among continents.
High Late Cretaceous sea level has been
attributed to high ocean-crust production rates
that resulted in more buoyant ridges displacing
seawater onto low-lying parts of continents
(‘‘tectonoeustasy’’) (20). This concept has been
extended to the Paleozoic through Early Meso-
zoic by assuming that 10
-year scale
continental flooding was caused by high sea-
floor spreading rates, even though direct evi-
dence for sea-floor spreading rates is absent
owing to subduction.
Our sea-level record for the past 100 My
has much lower amplitudes on the 10
-year scale than previously inferred (Figs.
2 and 3 and fig. S3), with implications for sea-
level change from 543 to 100 Ma. Our 100 to
7 Ma record (Fig. 2) is based on backstripping
stratigraphic data from five New Jersey coast-
al plain coreholes (21, 22). Similar estimates
obtained for each site suggest that we suc-
cessfully accounted for the effects of thermal
subsidence, sediment loading, compaction, and
water-depth variations. Our long-term trend in-
dicates that sea level was 50 to 70 m above
present in the Late Cretaceous (È80 Ma),
by È70 to 100 m since 50 Ma (23). This con-
trasts with previously reported Late Cretaceous
sea-level peaks of about 250 to 320 m based
on sea-floor spreading reconstructions (2), al-
though it is within error estimates of 45 to 365 m
(best estimate 230 m) (24). It is lower than
global continental flooding estimates [150 m
(19), 80 to 200 m (18)].
Our results are similar to backstripped
estimates from the Scotian and New Jersey con-
tinental shelves (14), although the Late Creta-
ceouspeakislower(50to70mversusÈ110 m)
(fig. S3). One-dimensional (1D) backstripping
may underestimate the Late Cretaceous peak
because coastal plain subsidence results from
athermoflexuraleffect(14), and thermal sub-
sidence curves may slightly overestimate the
tectonic portion of subsidence of the older sec-
tion. Considering backstripping and continental
flooding estimates (18, 19) and errors in our
paleowater depth estimates (eustatic error of
T10 to 35 m), we conclude that sea level in the
Late Cretaceous was 100 T 50 m higher than it
is today.
Using new sea-floor age data, Rowley (25)
suggested that there have been no changes in
sea-floor spreading rates over the past 180 My.
Our record implies a modest decrease in the
rate of ocean-crust production because the long-
term eustatic fall of 70 to 100 m since the early
Eocene (Fig. 3) cannot be totally ascribed to
permanent growth of ice sheets (26).
Fig. 2. Comparison of Phanerozoic backstripped eustatic estimates of this
study, Watts (14), Sahagian (35), Kominz (29), Levy (30), and Bond (18);
EPR records of Vail (10)andHaq(11, 16); continental flooding records of
Sloss (15) and Ronov (17) plotted versus area, and Bond (18), Harrison (19),
and Sahagian (4) plotted versus sea level; and evolutionary records compiled
by Katz (52).
Our observation that long-term eustatic
changes were appreciably smaller than previ-
ously thought has implications for geochemical
models [e.g., (27)] that have used sea-level
records to scale ocean production rates. Es-
timates derived from backstripping from the
past 170 My (Fig. 2) show much
lower long-term amplitudes than
those published by EPR. Back-
stripped sea-level records from the
Cambrian-Devonian of the western
United States show È200-m ampli-
tudes on the 10
-year scale (28–30)
(Fig. 2), although a Cambrian-
Ordovician backstripped data set
from the Appalachians shows a
lower (È70 m) amplitude (Fig. 2)
(28). The sea-level rise in the
Cambrian is attributed to the gen-
eration of new ocean ridges with
the breakup of Pannotia (29), but
the amplitude of this rise is still
uncertain. Although the jury is still
out on the amplitudes of Paleozoic
sea level on the 10
-year scale,
our work suggests that the EPR
records cannot be used to scale
past spreading rates.
Sea-level changes on very
long time scales (250 My) are
related to the assembly and break-
up of supercontinents. Formation
of the supercontinents Pannotia
(late Proterozoic to Early Cambri-
an) and Pangea (Permian to early
Triassic) was associated with low
levels of continental flooding (Fig.
2). This may be attributed to (i) a
eustatic effect due to thickening of
continents during orogeny result-
ing in increased oceanic area (2)
and/or (ii) higher elevations that
result when trapped heat builds up
below the supercontinents (31).
Million-Year Scale Changes
In 1977, EPR surprised academic
and industrial colleagues with the
publication of a Phanerozoic eustatic
record that showed more than 50
falls, some as large as 400 m (10). In
1987, the EPR group published a
series of papers, including a syn-
thesis in Science (11) that reported
more than 100 sea-level falls dur-
ing the past 250 My, with a max-
imum fall of 160 m. The EPR
studies came under intense scru-
tiny because of the novel sugges-
tions that (i) sequence boundaries are time-
important features that could be recognized on
seismic profiles and (ii) seismic profiles could
be used to determine the history of sea level.
The EPR curves have been strongly criticized
for their methodology (12, 32), with critics sug-
gesting that coastal onlap curves presented
cannot be translated into a eustatic estimate.
Drilling on the New Jersey margin has
provided new insights into the amplitudes of
and mechanisms for 10
-year scale sea-level
changes. Fourteen Late Cretaceous sequences
and 33 Paleocene-Miocene sequences were
identified in New Jersey coastal plain core-
holes (13, 33) and dated by integrating bio-
stratigraphy, Sr-isotopic stratigraphy, and
magnetostratigraphy to produce a chronology
with age resolution of better than T0.5Myfor
the Cenozoic (13)andT1.0MyfortheLate
Cretaceous (33). Onshore New Jersey se-
quence boundaries correlate with sequence
boundaries in the Bahamas, northwest Europe,
the U.S. Gulf Coast, Russia, offshore New Jer-
sey, and those of EPR, which suggests that
they are global and formed in
response to eustatic falls (13, 33).
Thus, drilling has validated the
number and timing, although
not the amplitude, of many of
the EPR sea-level events for the
past 100 My (13, 33). Oligocene-
Miocene sequence boundaries
can be firmly linked with global
O increases, demonstrating a
causal relation between sea level
and ice volume (13, 33), as ex-
pected for the Icehouse world of
the past 33 My.
Backstripping of the New
Jersey records provides eustatic
estimates from È100 to 7 Ma
(Fig. 3). Paleocene-Eocene and
Miocene estimates are derived
from 1D backstripped records
from five sites and Late Creta-
ceous sequences from two sites
(34). Several Upper Cretaceous
onshore sections capture full
amplitudes of change; howev-
er, many Cretaceous and most
Cenozoic onshore sections do
not record sea-level lowstands.
Eustatic estimates for the latest
Eocene to earliest Miocene are
derived from 2D backstripping
(22) that addressed this problem.
Our backstripped eustatic es-
timate (table S1) shows that
global sea level changed by 20
to 80 m during the Late Creta-
ceous to Miocene (this study)
and the Middle Jurassic to Late
Cretaceous (35). Our compari-
son shows that the amplitudes of
the EPR sea-level curve, includ-
ing the most recent update (16),
are at least 2.5 times too high
Eustatic changes with ampli-
tudes of 10s of meters in less
than 1 My pose an enigma for
a supposedly ice-free Green-
house world, because ice-volume
changes are the only known
means of producing such large
and rapid changes. Our record
(Fig. 3) quantifies high ampli-
tudes and rates of eustatic change (925 m in
G 1 My) in the Late Cretaceous to Eocene
Greenhouse world. Based on the sea-level
history, we have proposed that ice sheets
existed for geologically short intervals (i.e.,
lasting È100 ky) in the previously assumed
Fig. 3. Global sea level (light blue) for the interval 7 to 100 Ma derived by
backstripping data (21). Global sea level (purple) for the interval 0 to 7 Ma derived
from d
foraminiferal d
O synthesis from 0 to 100 Ma (red), with the scale on the
bottom axis in ° [reported to Cibicidoides values (0.64° lower than
equilibrium)]. The portion of the d
data from Miller (44) and fig. S1 recalibrated to the time scale of (71). The d
curve from 65 to 100 Ma is based on the data compiled by Miller (36) calibrated
to the time scale of (72). Data from 7 to 100 Ma were interpolated to a constant
0.1-My interval and smoothed with a 21-point Gaussian convolution filter using
Igor Pro. Pink box at È11 Ma is sea-level estimate derived from the Marion
Plateau (51). Heavy black line is the long-term fit to our backstripped curve
(23). Light green boxes indicate times of spreading rate increases on various
ocean ridges (57). Dark green box indicates the opening of the Norwegian-
Greenland Sea and concomitant extrusion of the Brito-Arctic basalts.
ice-free Late Cretaceous-Eocene Greenhouse
world (36). This view can be reconciled with
previous assumptions of an ice-free world.
Sea-level changes on the 10
-year scale were
typically È15 to 30 m in the Late Cretaceous-
Eocene (È100 to 33.8 Ma), suggesting growth
and decay of small- to medium-sized (10 to
15 10
) ephemeral Antarctic ice sheets
(36). These ice sheets did not reach the Ant-
arctic coast; as a result, coastal Antarctica and
deep-water source regions were warm even
though there were major changes in sea level
as the result of glaciation (36). These ice sheets
existed only during ‘cold snaps,’ leaving Ant-
arctica ice-free during much of the Greenhouse
Late Cretaceous to Eocene (36).
Sea-level changes on the 10
-year scale
occurred throughout the Phanerozoic. Studies
from the Russian platform and Siberia provide
backstripped records of 10
-year sea-level
changes that are remarkably similar to New
Jersey in the interval of overlap and extend to
the Middle Jurassic (È170 Ma) (35). The strat-
igraphic record before 170 Ma is replete in
-year sea-level changes (16, 37). However, it
is unclear whether these variations represent
global changes in sea level. Eustatic estimates
have been extracted from backstripping of Pa-
leozoic strata (28, 29) (Fig. 2), although differ-
ences in the Appalachian versus the western
U.S. Cambrian-Ordovician sea-level amplitude
estimates are large, and thus the eustatic imprint
is ambiguous.
Eustatic changes on the 10
scales were controlled primarily by variations
in ice volume during the past 100 My and
may be expected to be modulated by both
short-period [19/23 (precession), 41 (tilt), and
È100 ky (precession)] and long-period [1.2
(tilt) and 2.4 My (precession)] astronomical
variations (38). Spectral analysis of our sea-
level records shows that variations occur with
an as-yet-unexplained, persistent 3-My beat
and a second primary period varying from 6
to 10 My (fig. S4). Amplitudes in the È3-My
bandwith are È10mfrom60to20Ma,with
lower amplitude from 90 to 60 Ma.
The existence of continental ice sheets in the
Greenhouse world is a controversial in-
terpretation, but the study of ice-volume history
has progressively tracked ice sheets back through
the Cenozoic (36). After extensive debate, a
consensus has developed that ice volume
increased markedly in the earliest Oligocene
(8, 9). We suggest that, at that time, the Ant-
arctic ice sheet began to be a forcing agent of,
and not just a response to, ocean circulation
(36). The Antarctic continent (including west
Antarctica) (39) was entirely covered by ice, and
sea level was lower by È55 m (22). As a result,
latitudinal thermal gradients (40) and deep-water
circulation rates increased [with pulses of
Southern Component and Northern Component
Water (41)]. Diatoms diversified rapidly in
response to increased surface-water circulation
and nutrient availability (Fig. 2), resulting in
increased export production and a positive
feedback on CO
drawdown and cooling.
The earliest Oligocene event represented a
major change in climate state from a Greenhouse
world with cold snaps to the Icehouse world that
continues today. Sea-level changes from the
Oligocene to the early Pliocene (È33.8 to 2.5
Ma) were È30 to 60 m (Figs. 3 and 4), with
growth and decay of a large (up to present
volumes of 25 10
) ice sheet mostly in
Antarctica. A middle Miocene d
associated with deep-water cooling and two
ice-growth events that resulted in the permanent
development of the East Antarctic ice sheet
(40). Northern hemisphere ice sheets (NHIS)
have existed since at least the middle Miocene
(41), but large NHIS with sea-level changes of
60 to 120 m only began during the late Pli-
ocene to Holocene (È2.5to0Ma)(Fig.4).
Milankovitch Scale Changes
The growth and decay of NHIS (the late
Pliocene-Holocene ‘ice ages’’) and attendant
sea-level changes were paced by 10
year scale Milankovitch changes. The d
record shows a dominant 100 ky (eccentricity)
beat over the past 800 ky, with secondary 19/23
(precession) and 41-ky (tilt) periods (42). Be-
fore È800 ky, the tilt cycle dominated d
(43) and sea-level records. Although strong
precessional and eccentricity beats occur in the
carbon system, the tilt cycle has dominated
O and ice-volume records for much of the
past 33.8 My (9). Growth and decay of small-
to medium-sized ice sheets in the Late
Cretaceous-Eocene on the Milankovitch scale
probably lie near or below the detection limit
of d
O records [È 0.1 per mil (°) 0 10-m
eustatic change].
Continental margins record 10
imentation rate settings. Foraminiferal d
records reflect ice volume in addition to tem-
perature changes and potentially provide a
proxy for sea-level changes on the 10
-year scale. The d
O record provides con-
tinuity and excellent age control, although
assumptions about thermal history must be
made to use it as a sea-level proxy. In addition,
diagenesis complicates planktonic foraminiferal
O records, although benthic foraminifera
generally show little evidence for diagenesis
at burial depths less than 400 to 500 m (44).
We derive sea-level estimates from 9 to
0 Ma using benthic foraminiferal d
O records
because the New Jersey record is incomplete
from 7 to 0 Ma (table S1). We scaled the ben-
thic foraminiferal d
by making minimum assumptions about ocean
thermal history (Fig. 4). The resultant sea-level
curve (Fig. 4) aligns remarkably well with the
backstripped record from 9 to 7 Ma (Fig. 3).
Our d
O-derived sea-level estimate for the
past 9 My (Fig. 4) shows that the record is
dominated by the response to the 41-ky peri-
od tilt forcing, which increases in amplitude
toward the present, and a low-amplitude È21-ky
precession response. The major 100-ky events
of the past 900 ky stand out in the sea-level
record (Fig. 4). There are prominent 10
scale sea-level falls (the 2.5, 3.3, 4.0, 4.9, 5.7,
and 8.2 Ma events) (Fig. 4), but these are not
obviously paced by amplitude modulations of
either precession or tilt (fig. S4).
Suborbital Scale
Very large (9100 m) sea-level rises are associ-
ated with glacial terminations of the past 800 ky
(fig. S1) (6).Themostrecentrisethatfollowed
the last glacial maximum at 18 ka occurred
as two major steps associated with meltwater
pulses (MWP) 1a (13.8 ka) and 1b (11.3 ka),
punctuated by a slowing at È12 ka (6). Sea-
level rise slowed at about 7 to 6 ka (fig. S1).
Some regions experienced a mid-Holocene sea-
level high at 5 ka, but we show that global sea
level has risen at È1 mm/year over the past 5
to 6 ky. We present new core data from New
Jersey covering the past 6 ky that show a rise
of 2 mm/year over the past 5 ky (fig. S1). This
New Jersey curve is remarkably similar to
sea-level records from Delaware (46) and south-
ern New England (47), with a eustatic rise of
1 mm/year over the past 5 ky once corrected
for subsidence effects (48), virtually identical
to that obtained from Caribbean reef localities
(49) (fig. S1) accounting for subsidence.
Error Estimates
Long-term sea-level estimates show consider-
able differences, with a large range of Late
Cretaceous sea-level estimates: È110 m (14),
150 m (19), 250 m (4),and80to200m(18),
and our best estimate of 100 T 50 m. We con-
clude that sea-level amplitudes on this scale
were substantially lower than generally believed
(100 versus 250 m) over the past 170 My, with
uncertain amplitude before this (Fig. 2).
Sea-level estimates on the 10
-year scale
have an uncertainty, typically, of at best T10 to
T50 m. The two main sources of errors in
backstripping relate to hiatuses (time gaps) and
paleowater depth estimates. New Jersey coastal
plain sequences represent primarily inner-shelf
to middle-shelf environments, with eustatic
errors from paleowater depth estimates of T10
to 20 m (50). Hiatuses in our record potentially
explain why amplitudes of change might not be
fully recorded, and the effect of hiatuses can be
evaluated only by comparing our record with
other regions. Drilling on the Marion Plateau
(offshore northeast Australia) targeted an È11 Ma
eustatic lowering (51); backstripping yields a
sea-level estimate of 56.5 T 11.5 m for this
event (pink bar on Fig. 3). Our estimate for
this event is È40 T 15 m (Fig. 1); these esti-
mates are consistent, within error, but suggest
that we may underestimate sea-level falls by 5
to 30 m.
The record of the past 130 ky illustrates the
errors in converting a d
O record into a sea-
level proxy (fig. S1). Benthic foraminiferal
O records can be scaled to a faithful proxy
for glacial to cool interglacials [Marine Isotope
Chron (MIC) 2d to 5d] (fig. S2), with sea level
and d
O in phase and lagging insolation.
However, large deviations of the d
sea-level curve occur during peak warm in-
tervals (Holocene and MIC 5e) (Fig. 2), with a
hint that deep-sea temperature change leads
sea level. We have attempted to correct for this
temperature effect by scaling to the
Barbados sea-level record (6). How-
ever, this results in underestimating
amplitudes of glacials and overesti-
mating amplitudes of interglacials,
with a resultant 20% uncertainty.
Relation of Sea Level to
Evolution and Climate
Episodes of supercontinent rifting
and sea-level rise on the 10
-year scale played a role in
phytoplankton evolution since the
Proterozoic by flooding continental
shelves and low-lying inland areas
and increasing the total length of
coastline. The resulting increases in
habitat heterogeneity, ecospace, and
nutrient availability favored plankton
that lived along continental margins.
Accordingly, diversity increases in
phytoplankton (Fig. 2) appear to
correlate with continental rifting of
Pannotia (Early Paleozoic) and
Pangea (Jurassic) (Fig. 2), ultimate-
ly resulting in the three groups of
eukaryotic phytoplankton (cocco-
lithophores, diatoms, and dinoflag-
ellates) that dominate the modern
ocean (52).
Sea-level changes are expected
with beats of 19/23, 41, and 100 ky,
but similar changes on the 10
scale (Fig. 3) have puzzled geolo-
gists. Sea-level cyclicity on the 10
year scale can be explained by a
modulation of the shorter term
Milankovitch-scale sea-level events
(fig. S5). For example, a promi-
nent seismic disconformity spanning
the Oligocene/Miocene boundary
(È23.8 Ma) on the New Jersey slope (13)
can be correlated to a detailed d
O record at
deep-sea Site 929 (53), showing that the 10
year scale sea-level fall at the Oligocene/
Miocene boundary occurred as a series of
41-ky d
O increases and sea-level changes.
The 41-ky sea-level falls are reflected in core
photographs by a series of dark-light changes
(fig. S5), resulting from variations in glauco-
nite transported downslope during lowstands.
The seismic reflection is a concatenation of
these beds and the ice-volume events that
caused them.
The high sea levels of the Late Cretaceous
and early Eocene are associated with peak ben-
thic foraminiferal d
O values (Fig. 3) (table
S1), and it has long been suggested that sea
level covaries with d
O on the 10
-year scale
[e.g., (54)]. On the 10
-year scales, such
covariance can be explained by ice-volume
changes in concert with temperature changes
(8, 13). However, this cannot be true on the
-year scale because most of the
O signal must be attributed to temperature
changes. For example, 3.6° of the 4.4°
increase from 50 to 0 Ma (Fig. 3) must be
attributed to deep-water cooling (15-C overall)
rather than to ice storage (55). The link
between sea level and temperature on the
-year scale cannot be due to cooling
alone, because this would explain only È15 m
of eustatic fall since 50 Ma. The link between
O and sea-level variations on the 10
-year scale can be explained by CO
variations controlled by tectonics (changes in
ocean-crust production and mountain uplift).
High ocean-crust production rates have
long been linked to high sea level, high CO
and warm global temperatures [e.g., (54)]. Warm
Late Cretaceous climates and elevated sea
level may be attributable to moderately high-
er sea-floor production rates, although our
results require that crustal production rates
were lower than previously thought. However,
the intensity of spreading ridge hydrothermal
activity (a major source of CO
appears also to correlate with
times of major tectonic reor-
ganizations (56). We propose that
the early Eocene peak in global
warmth and sea level (Fig. 3) was
due not only to slightly higher
ocean-crust production but also to
a late Paleocene-early Eocene tec-
tonic reorganization. The largest
change in ridge length of the past
100 My occurred È60 to 50 Ma
(57), associated with the open-
ing of the Norwegian-Greenland
Sea, a significant global reor-
ganization of spreading ridges,
and extrusion of 1 to 2 10
of basalts of the Brito-
Arctic province (58). A late
Paleocene to early Eocene sea-
level rise coincides with this
ridge-length increase, suggesting
a causal relation. We suggest
that this reorganization also in-
creased CO
outgassing and
caused global warming to an
early Eocene maximum. Subse-
quent reduced spreading rates
and hydrothermal activity re-
level, reduced CO
and a cooling of deep-water by
È8-C(44). CO
may have been
further lowered by an increase in
continental weathering rates dur-
ing the remainder of the Cenozo-
ic (59), explaining an additional
deep-water cooling of 7-Cto
Our studies of the past 100
My provide clues to the tempo of
climate and ice-volume changes
for other Icehouse and Green-
house worlds of the Phanerozoic (Fig. 2).
Icehouse worlds of the past 33 My, the Penn-
sylvanian to Early Permian, Late Devonian,
and Late Ordovician (60), can be characterized
by ice-volume changes that caused sea-level
variations up to 200 m. Greenhouse worlds
characterize much of the Phanerozoic, but we
note that small (10 to 15 10
), ephem-
eral ice sheets occurred in the Greenhouse of
the Late Cretaceous to Eocene. This raises
the question as to whether any portion of the
Fig. 4. Oxygen isotopic-based sea-level estimate for the past 9 My.
Isotopic values are reported to equilibrium, with coretop and last glacial
maximum values indicated with arrows and thin vertical green lines. Thin
black line is raw data plotted versus the d
O scale (bottom). The purple
line is the sea-level estimate (top scale), which is derived by correcting
the d
O data by 0.5° due to a È2-C cooling between 3.3 and 2.5 Ma
(red line), scaling by d
O to sea level using a calibration of 0.1°/10 m,
and scaling the result by 0.8 (45).
Phanerozoic was ice-free. The Triassic and
Cambrian pose two of the best candidates for
an ice-free world (60), yet Haq (11, 16) noted
numerous 10
-year scale sea-level variations
at these times (Fig. 2). If corroborated, these
changes suggest the presence of ephemeral ice
sheets even in the warmest of the Greenhouse
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OCE 0084032, EAR97-08664, EAR99-09179, and
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Supporting Online Material
Figs. S1 to S5
Table S1
Supporting Online Material for
The Phanerozoic Record of Global Sea-Level Change
Kenneth G. Miller,* Michelle A. Kominz, James V. Browning, James D. Wright,
Gregory S. Mountain, Miriam E. Katz, Peter J. Sugarman, Benjamin S. Cramer,
Nicholas Christie-Blick, Stephen F. Pekar
*To whom correspondence should be addressed:
Published 25 November 2005, Science 310, 1293 (2005)
DOI: 10.1126/science.1116412
This PDF file includes:
Figs. S1 to S5
Table S1
Figure Captions (Supplementary Online Material)
Fig. S1. Compilation of Holocene relative sea-level records from the western North Atlantic.
Records are from New Jersey (blue/green symbols from this study and red symbols from N.
P. Psuty, Physical Geography, 7, 156 (1986), Delaware (46)southern New England (47), and
a Caribbean reef compilation (49) with a polynomial fit from 8-0 ka (6) and a linear fit from
5-0 ka (this study).
Fig. S2. Comparison sea-level record from the Huon New Guinea terraces (7) and Barbados (6)
and benthic foraminiferal δ
O record from Pacific (Carnegie Ridge) core V19-30 (N. J.
Shackleton, N. G. Pisias, in The Carbon Cycle and Atmospheric CO
, E. T. Sunquist, W. S.
Broecker, Eds. (American Geophysical Union, Washington, D.C., 1985), pp. 303-317.). Grey
curve at bottom shows variations in insolation for June at 65°N latitude. 0 is modern sea
Fig. S3. Comparison of the sea-level estimate and δ
O record from Figure 3 with the sea-level
record of Haq (11), the long-term record of Watts (14) from backstripping of the Scotian
shelf and New Jersey outer continental shelf, and the backstripped record of Sahagian (35)
from the Russian platform and Siberia. Note that the scale for the Haq estimates (green axis)
is 2 times that of our sea-level estimate (blue line and axis). Watts and Sahagian curves are
plotted using the blue axis.
Fig. S4. Spectral content of the sea-level curve. The sea-level curve is shown at the top in black,
with a 0.1 my Gaussian interpolation that was used for spectral analysis shown in red. To the
right is the periodogram of the data in black with the expected red noise spectrum in red. The
image shows variation in spectral power through time calculated using the Gaussian Wigner
Transform implemented by Igor Pro™. Spectral power is indexed to colors according to the
scale in the upper right. Note that the vertical period and frequency axis are log
scales, but
with tick marks at linear intervals.
Fig. S5. Benthic foraminiferal δ
O data (13) from Ocean Drilling Program Site 904 (NJ
continental slope) plotted versus depth showing magnetic chronozone, core photographs,
reflectivity, and core log impedance. Also shown are δ
O records from South Atlantic Site
929 (53) that allow correlation to the Site 904 record. Red curve is plotted versus depth while
the black is plotted versus age scale.
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Geol. Bull. 80, 1433 (1996).
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49. R. G. Lighty, I. G. Macintyre, R. Stuckenrath, Coral Reefs 1, 125 (1982).
53. J. C. Zachos, B. P. Flower, H. Paul, Nature 388, 567 (1997).
Age, yr
Depth, m
New Jersey = 1.9 mm/yr
So. New England
Holocene Sea Level,
Western North Atlantic
Reefs regression =
1.26 mm/yr
Miller et al., Science, Fig. S1
Caribbean Reefs
other New JerseyIsland Beach
other New JerseyGreat Bay 2
Union BeachCape May
Great BayGreat Bay 1
CheesequakeRainbow Island
O ‰
Elevation (m)
0 50 100 150
Age (ka)
New Guinea
Oxygen isotopes, V19-30
Miller et al., Science, Fig S2
Miller et al., Science Fig. S3
Age (Ma)
Late Cretaceous
e. l.
NP Zones
NN Zones
CC Zones
-50 0 50 100 150-100
large NHIS
Large Antarctic Ice Sheets
Small Antarctic Ice Sheets
Merch III
Haq sea Level (m)
Sea Level (m)
-200 0 200
Miller et al., Science, Fig. S4
Reflectivity coefficient
Gray scale
ages (Ma)
Hole 904A
-0.02 0.02
reflection m6
Miller et al., Science, Fig. S5
Depth (mbsf) (Site 904A)
Age (Ma) (Site 929 only)
Hole 904A
vs. depth
12 0
Site 929,
vs. age
Cores 33 and 34
... The Cretaceous period presents a substantial rise of global temperature, that caused a reduction of ice in the poles and the spreading of the Atlantic Ocean floor, resulting in a dramatic rise in the sea-level that reached its highest point in the Turonian-Cenomanian (Miller et al., 2005;Tennant et al., 2017). An episodic increase in diversity of marine faunas has been suggested for the Late Cretaceous, and neoselachian diversity seems to follow this pattern (Underwood, 2006;Kriwet et al., 2009a;Guinot et al., 2012). ...
... These divergence events coincide with the rapid recovery in neoselachian diversity after the Cretaceous-Paleocene (K/Pg) boundary (Underwood, 2006;Guinot et al., 2012) and with the global climate changes during the Paleocene, shifting from a warmer earth with high sea levels during the Eocene to a colder climate with glaciation in the Oligocene (Miller et al., 2005). This reduction of Earth's temperature is attributed to continental movement, which resulted in the Northward drift of Australia and India, the opening of the Drake Passage, and the establishment of the circum-Antarctic current, leading to the thermal isolation of Antarctica (Ehrmann and Mackensen, 1992). ...
We present a time-scaled analysis based on morphological characters to estimate the divergence ages for the major batoid clades. Two approaches were used: tip-dating, which allows the extinct taxa to be included as terminals, assessing the phylogenetic relations and their divergence time simultaneously; and basic and minimum branch length ('a posteriori' methods) that date a pre-existing unscaled topology, given a set of stratigraphic data for the taxa involved. We used stratigraphic indexes to compare the divergence ages recovered by both methods. The tip-dating approach obtained a more resolved topology and slightly better stratigraphic index scores than the other methods. Overall the tip-dating analysis recovered slightly earlier divergence ages than the rest of the time dating analyses and the known fossil record of the groups. However, these divergence ages were not as old as those estimated by molecular analysis. Our results suggest the diversity increase through the Late Jurassic-Early Cretaceous might not be gradual, and that Early Cretaceous diversity could be significantly higher. As several divergence events are placed in the Early Cretaceous, there is a suggestion that an active period of cladogenesis leads to the Late Cretaceous high diversity. The last divergence events recovered by the present analysis occurred in the Paleogene and led to the extant groups of batoids.
... The origin of Anatidae s. l. may be associated (Zelenkov, 2018) with the global sea-level drop in the late Eocene (Miller et al., 2005), which led to shallowing of the epicontinental sea basins in the Asian part of Eurasia and the appearance of extensive shallow waterbodies. A large area of shallow waterbodies, in particular, was characteristic of the Ferghana Bay (Ferghana-Tajik basin) of the Eocene Turan Sea (Nevesskaya, 1999), which reached the Tarim Depression in western China in the middle of the Eocene (Popov et al., 2009). ...
Full-text available
An analysis of the Eurasian Cenozoic (late Eocene-Neogene) fossil record of anatids (Anatidae s. l.; including Romainvilliinae and Dendrocygninae) is presented. The evolutionary origin of Anatidae s. l. may be associated with the appearance of large shallow waterbodies in Asia during the Late Eocene as a result of the fall in the global sea level and the resulting retreat of the epicontinental seas. Four major temporal stages can be recognized in the evolution of the Cenozoic Eurasian anatids communities, without any traceable continuity between particular stages (at the current stage of knowledge). Some recent anatid genera (e.g., Tadorna) first appear in the paleontological record at the level of the early and middle Miocene (17-15 Ma), but temperate faunas of essentially modern ecological composition became widespread only in the late Mio-cene (9-6 Ma). The details of transitions between various faunistic stages, as well as the origin of modern communities, remain largely unstudied.
... Numerical simulations suggest that the intensification of the Atlantic meridional overturning circulation associated with the EOT also caused a northward shift of the Inter Tropical Convergence Zone (ITCZ), increasing precipitation over northern Africa (Elsworth et al., 2017). The inception of Antarctic glaciation is also thought to have produced a 70-m sea-level drop (Miller et al., 2005). Meanwhile, the growth of the Hoggar swell in northern Africa ( Fig. 2B, C) led to the establishment of a modern-like west African drainage geometry (Grimaud et al., 2017). ...
Full-text available
Tropical Africa is home to an astonishing biodiversity occurring in a variety of ecosystems. Past climatic change and geological events have impacted the evolution and diversification of this biodiversity. During the last two decades, around 90 dated molecular phylogenies of different clades across animals and plants have been published leading to an increased understanding of the diversification and speciation processes generating tropical African biodiversity. In parallel, extended geological and palaeoclimatic records together with detailed numerical simulations have refined our understanding of past geological and climatic changes in Africa. To date, these important advances have not been reviewed within a common framework. Here, we critically review and synthesize African climate, tectonics and terrestrial biodiversity evolution throughout the Cenozoic to the mid-Pleistocene, drawing on recent advances in Earth and life sciences. We first review six major geo-climatic periods defining tropical African biodiversity diversification by synthesizing 89 dated molecular phylogeny studies. Two major geo-climatic factors impacting the diversification of the sub-Saharan biota are highlighted. First, Africa underwent numerous climatic fluctuations at ancient and more recent timescales, with tectonic, greenhouse gas, and orbital forcing stimulating diversification. Second, increased aridification since the Late Eocene led to important extinction events, but also provided unique diversification opportunities shaping the current tropical African biodiversity landscape. We then review diversification studies of tropical terrestrial animal and plant clades and discuss three major models of speciation: (i) geographic speciation via vicariance (allopatry); (ii) ecological speciation impacted by climate and geological changes, and (iii) genomic speciation via genome duplication. Geographic speciation has been the most widely documented to date and is a common speciation model across tropical Africa. We conclude with four important challenges faced by tropical African biodiversity research: (i) to increase knowledge by gathering basic and fundamental biodiversity information; (ii) to improve modelling of African geophysical evolution throughout the Cenozoic via better constraints and downscaling approaches; (iii) to increase the precision of phylogenetic reconstruction and molecular dating of tropical African clades by using next generation sequencing approaches together with better fossil calibrations; (iv) finally, as done here, to integrate data better from Earth and life sciences by focusing on the interdisciplinary study of the evolution of tropical African biodiversity in a wider geodiversity context.
... During Albian and Cenomanian, the sea level rose prominently, and the sedimentary record displays peculiar facies testifying to equally peculiar processes that have not been observed during other periods (e.g. Giorgioni et al., 2015;Haq et al., 1988;Hardenbol et al., 1998;Hay, 2008;Miller et al., 2005). They were characterized by very high temperatures, long-term rising sea level and formation of oceanic gateways and seaways (Giorgioni et al., 2015). ...
The Agadir Basin (Moroccan Atlantic margin) is characterized by its fossil richness, including organic-walled microfossils. The palynological analysis of the middle Cretaceous succession from the Tamzargout section and EGA.1 well reveals the presence of well-preserved and diverse assemblage, rich in dinoflagellate cysts. The assemblages contain stratigraphic marker taxa and show significant chronostratigraphic events. Based on these bioevents and on the comparison with different palaeogeographic domains, a determination of age was proposed. The biogeographic characteristics of most cosmopolitan taxa in this study confirm the establishment of new oceanic communication related to the opening of the equatorial Atlantic. The Albian-Cenomanian transition has been recognized only in EGA.1 well, whereas the Aptian-Albian transition, the early-mid Albian and the mid-late Albian have been defined in both the section and the well. The recorded associations are comparable to those of neighboring deposits and those of the Tethyian and Atlantic domains. The vertical distribution of the organic matter in the sediments of the Agadir Basin and the compilation of all palaeoenvironmental proxies allowed identifying an Albian transgression with specific palaeoenvironments in each interval. Neritic marine environments alternated with short phases of continental and oceanic influence is deduced for the late Aptian-early Cenomanian in this basin. The late Aptian-early to mid Albian recorded an outer neritic palaeoenvironment under oceanic influence; the mid to late Albian showed littoral conditions during a regressive phase fluctuating to middle to outer neritic environment; finally the late Albian-early Cenomanian transition was characterized by a middle neritic palaeoenvironment under coastal influence.
... In this context (subsidence and sea-level drops and rises), marine deposits should have been preserved in a borehole crossing a 0-100 m range of elevation below the sea level. The sea-level have oscillated only between 50 and -50 m during the Early Pleistocene (Miller et al., 2005;de Boer et al., 2010;Rohling et al., 2014). The base of the GBEC5-2 borehole (at least from − 67 m depth) should thus be constituted by marine deposits, even during lowstands. ...
... By the end of the Miocene, moist dipterocarp forests, which had persisted across India since the Eocene, withdrew to the Western Ghats (Rust et al., 2010;Shukla et al., 2013) as the climate of the south-eastern region of the peninsula and the north-western region of Sri Lanka became progressively more seasonal and arid, as it remains even today. Thus, even though greatly lowered sea levels gave rise to a ~200-km-wide isthmus connecting India and Sri Lanka for much of the Plio-Pleistocene (Anonymous, 1977;Miller et al., 2005), this appears to have served more as a filter than a corridor for the dispersal of taxa adapted to perhumid forests (Bossuyt et al., 2004). The town of Mannar, which lies on the Sri Lankan side of the erstwhile isthmus, today receives a monthly average rainfall of <50 mm for more than half of the year, whereas the island's perhumid south-west has no months with an average rainfall of <100 mm (Somasekaram et al., 1988). ...
The South and SouthEast Asian freshwater fish genus Systomus (Cyprinidae) comprises 17 valid species. Six nominal species, including three endemics, have been reported from Sri Lanka, a continental island separated from India by a shallow-shelf sea. The species diversity of Systomus on the island has until now not been assessed; neither has an evaluation been made of their phylogenetic history. Here, based on an analysis of the nuclear recombination activating protein 1 (rag1), and mitochondrial cytochrome c oxidase subunit 1 (cox1) and cytochrome b (cytb) gene markers, and a morphological examination of 143 specimens from 49 locations in Sri Lanka, we reassess the diversity of Systomus on the island and analyse patterns of their evolution and biogeography. Divergence-time estimates, based on a substitution rate calibration , date the basal split between Systomus and its sister group, the Afrotropical small barbs, to 30.0 Ma (95% highest posterior density: 25.4-35.2 Ma). The species of Systomus belong to two distinct clades. The first includes the Sri Lankan endemics S. asoka, S. martenstyni and S. pleurotaenia, which comprise an insular diversification following the immigration of a common ancestor during the Oligocene. The second, which includes the remaining species of Indian, Sri Lankan and SouthEast Asian Systomus, has a crown age dating to the Late Miocene. Morphological and molecular species delimitation analyses failed to validate the two nominal species, S. spilurus and S. timbiri, previously reported from Sri Lanka: both are considered synonyms of S. sarana, as are the nomina S. chryseus, S. chrysopoma, S. laticeps, S. rufus, S. pinnauratus and S. subnasutus. Four genetically and geographically discrete line-ages of S. sarana occur in the island, and three in India. Molecular species delimita-tion analysis suggests these all belong to a single species, S. sarana. The genetically distinct Sri Lankan populations of S. sarana result from Plio-Pleistocene dispersal or vicariance events between India and Sri Lanka-as a result of emergence and in-undation of the now submerged isthmus connecting the two landmasses-as well as autochthonous insular diversification.
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Parts of the presentation: (1) Prologue: My personal involvement with climate; (2) Weather and climate: Definitions, meaning and historical background; (3) Climate of the past; (4) Climate of the present; (5) Basics of climate theory; (6) The energy cycle; (7) The carbon cycle; (8) The hydrological cycle and its alleged intensification; (9) The alleged intensification of hydrological extremes; (10) Dealing with the future of climate and water; (11) Epilogue: Is our future dark?
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This work reconstructs the complex evolution of a coastal wedge in response to Pliocene tectonic activity and Pleistocene climate change recorded in the upper Neogene subsurface succession of the Friulian-Venetian Basin (FVB), since the latest Messinian sea-level drop event to the late Pleistocene. The FVB is the north-eastern portion of the wider Po Plain-Adriatic foreland basin (Northern Italy), which bounds to the east the whole Italian peninsula and is the place where most of the Italian hydrocarbon offshore fields presently occur. Also, the city of Venice and its surrounding lagoon is presently one of the sites most sensitive to land subsidence worldwide and even a few mm loss of ground elevations can significantly change the natural lagoon environments and threaten the city's survival. To this purpose, we have integrated seismics and well logs analysis with 1D-geohistory modelling on wells, using corrected paleobathymetric data, in order to extract decompacted sedimentation rates. The new age model is based on a complete chronostratigraphic revision of the continuously cored Venezia 1 well, correlated with other 12 hydrocarbon wells to form proper geological depth-calibrated profiles across the basin. Results suggest a major tectonic control on marine sedimentation and basin accommodation space changes during the entire Pliocene-early Pleistocene time, influenced by the Northern Apennines thrust fronts migration. On the contrary, the mid-upper Pleistocene deposition, characterized by a weak deformation, is mainly controlled by climate and basin geometry. During the early mid Pleistocene, an impressive progradational cycle (in the literature usually named “Sabbie di Asti group”) followed the deposition of deep-water turbidites; in this work, we subdivide the different clastic bodies the formation is made of. The uppermost part of the “Sabbie di Asti group” is dominated by shallow-water to continental deposits showing a prominent regressive-transgressive cyclicity, where unfortunately chronological ties are limited. Nevertheless, 6 main cycles driven by 100 kyr Milankovitch-type ciclicity, were laterally correlated by means of the well electric logs and linked to marine ∂18O isotope and eustatic curves.
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Latakia Ridge Basin has a critical location in northwestern Syria as part of a remnant of collision zone between the Eurasian and Afro-Arabian plates. The basin contains up to 3000m of Late Maastrichtian-Recent sediments. The bitumen-rich beds occur in the Middle Eocene succession. Within the basin, the thicknesses of this interval vary (15m-350m), reflecting the structural history of the basin that formed after the obduction of external Late Maastrichtian-aged Baer-Bassit Ophiolitic Massive. Al-Kornish Al-Janoubi section in the City of Latakia, close to the Eastern Mediterranean, show the Middle Eocene organic-rich Carbonates. The detailed study of this succession is a necessary step leading to reconstructing of geological structures that may be targets for oil prospecting. The exposed succession consists mainly of rhythmic alternation of chalky limestone and marl, some of which show soft-sediment deformation structures (SSDS), and contains large-scale slumps, that consist of sets of turbidites. This field-based study focuses on the Middle Eocene carbonates in Al-Kornish Al-Janoubi section and provides new insights on the depositional environment of this area. Soft-sediment deformation structures and facies interpretation results were combined to show that the Middle Eocene carbonate sequence was deposited as part of lobes of turbidites in a deep marine environment that formed part of a remnant basin with a compressional tectonic regime.
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This review demonstrates the benefit of numerical tidal modelling, calibrated by integrated comparison to the preserved stratigraphic record, and offers a refined classification and prediction of shoreline process regimes. Wider and consistent utilisation of these concepts, and numerical simulations of other depositional processes, will further improve process-based classifications and predictions of modern and ancient shoreline systems.
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Leg 81 drilling results on the west margin of Rockall Plateau, combined with available geophysical data, provide the first transect of the 'dipping reflector' type of passive margin. Unlike passive margins characterized by large tilted fault blocks, this type is characterized by an oceanward dipping suite of reflectors and may be the predominant type of rifted margin. The 'dipping reflector' margin can be divided into four structural zones: the ocean crust (Zone I), an outer high (Zone II), the area of dipping reflectors (Zone III), and a 'landward' zone (Zone IV) of subhorizontal reflectors. The Leg 81 transect sampled Zones II, III, and IV at four sites. The Leg 81 results neither prove nor disprove that the dipping reflectors are underlain by oceanic or continental crust, although preliminary gravity interpretation favors the latter. However, the Leg 81 results provide data and in turn constraints on reasonable models for the formation of this type of margin. -from Authors
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Commonly it is assumed that the intensity of mid-ocean ridge hydrothermal activity should correlate with spreading rate, since high spreading rates are an indication of large subcrustal heat sources needed for intense hydrothermal activity. We have tested this hypothesis by modeling the deposition of hydrothermal precipitates from cores from Deep Sea Drilling Project Leg 92, taken on the west flank of the East Pacific Rise at 19°S. Although spreading rates at the East Pacific Rise and its predecessor, the Mendoza Rise, have varied by only 50% in the last 30 million years, we found certain episodes, at about 25, 18, 14, and 9 million years ago, of hydrothermal manganese deposition as much as a factor of 20 higher than equivalent Holocene accumulation. These eposides do not correlate with spreading rate changes and instead seem to occur at times of major tectonic reorganizations. We propose that ridge jumps and changes of ridge orientation may substantially increase hydrothermal activity by fracturing the ocean crust and providing seawater access to deep-seated heat sources.
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Throughout the latter half of the Pleistocene epoch of Earth history, beginning ∼900 kyr ago, the climate system has been dominated by an intense oscillation between full glacial and interglacial conditions. During each glacial stage, global sea level fell by ∼120 m on average, as extensive ice sheets formed and thickened on the surfaces of the continents at high northern (primarily) and southern latitudes. Within each cycle this glaciation phase lasted ∼90 kyr and was followed by a much more rapid deglaciation event which terminated after ∼10 kyr and which returned the system to the interglacial state. The period of the canonical glacial cycle has remained very close to 100 kyr since its inception in mid-Pleistocene time. Because of the magnitude of the mass that was redistributed over the surface of the Earth during each such glacial cycle and because of the viscoelastic nature of the rheology of the planetary mantle, these shifts in surface mass load induced variations in the shape of the planet that have been indelibly transcribed into the geological record of sea level variability. Indeed, the geological, geophysical, and even astronomical signatures of this process, which is continuing today, are now being measured with unprecedented precision using the methods of space geodesy and have thereby begun to provide important new scientific insight and understanding, both of the interior of the solid Earth and of the climate system variability with which the ice ages themselves are associated. In this article my purpose is to bring together, in a single review, an assessment of where we currently stand scientifically with regard to understanding both of these aspects of the ice ages. Although the discussion will not address in any detail the fascinating issue of ice age climate, since this topic is sufficiently complex of itself to require a detailed review of its own, I will nevertheless attempt to briefly summarize the current state of understanding of the physical processes that are responsible for the occurrence of the ice age cycle, by way of providing a more complete context in which to appreciate the main lines of argument that will be developed.
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δ18Obenthic values from Leg 194 Ocean Drilling Program Sites 1192 and 1195 (drilled on the Marion Plateau) were combined with deep-sea values to reconstruct the magnitude range of the late middle Miocene sea-level fall (13.6 11.4 Ma). In parallel, an estimate for the late middle Miocene sea-level fall was calculated from the stratigraphic relationship identified during Leg 194 and the structural relief of carbonate platforms that form the Marion Plateau. Corrections for thermal subsidence induced by Late Cretaceous rifting, flexural sediment loading, and sediment compaction were taken into account. The response of the lithosphere to sediment loading was considered for a range of effective elastic thicknesses (10 < T e < 40 km). By overlapping the sea-level range of both the deep-sea isotopes and the results from the backstripping analysis, we demonstrate that the amplitude of the late middle Miocene sea-level fall was 45 68 m (56.5 ± 11.5 m). Including an estimate for sea-level variation using the δ18Obenthic results from the subtropical Marion Plateau, the range of sea-level fall is tightly constrained between 45 and 55 m (50.0 ± 5.0 m). This result is the first precise quantitative estimate for the amplitude of the late middle Miocene eustatic fall that sidesteps the errors inherent in using benthic foraminifera assemblages to predict paleo water depth. The estimate also includes an error analysis for the flexural response of the lithosphere to both water and sediment loads. Our result implies that the extent of ice buildup in the Miocene was larger than previously estimated, and conversely that the amount of cooling associated with this event was less important.
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We present an integrated geomagnetic polarity and stratigraphic time scale for the Triassic, Jurassic, and Cretaceous periods of the Mesozoic Era, with age estimates and uncertainty limits for stage boundaries. The time scale uses a suite of 324 radiometric dates, including high-resolution Ar-40/Ar-39 age estimates. This framework involves the observed ties between (1) radiometric dates, biozones, and stage boundaries, and (2) between biozones and magnetic reversals on the seafloor and in sediments. Interpolation techniques include maximum likelihood estimation, smoothing cubic spline fitting, and magnetochronology. The age estimates for the 31 stage boundaries (in mega-annum) with uncertainty (millions of years) to 2 standard deviations, and the duration of the preceding stages (in parentheses) are Maastrichtian/Danian (Cretaceous/-Cenozoic) is 65.0 +/- 0.1 Ma (6.3 m.y.), Campanian/Maastrichtian is 71.3 +/- 0.5 Ma (12.2 m.y.), Santonian/Campanian is 83.5 +/- 0.5 Ma (2.3 m.y.), Coniacian/Santonian is 85.8 +/- 0.5 Ma (3.2 m.y.), Turonian/Coniacian is 89.0 +/- 0.5 Ma (4.5 m.y.), Cenomanina/Turonian is 93.5 +/- 0.2 Ma (5.4 m.y.), Albian/Cenomanian is 98.9 +/- 0.6 Ma (13.3 m.y.), Aptian/Albian is 112.2 +/- 1.1 Ma (8.8 m.y.), Barremian/Aptian is 121.0 +/- 1.4 Ma (6.0 m.y.), Hauterivian/Barremian is 127.0 +/- 1.6 Ma (5.0 m.y.), Valanginian/Hauterivian is 132.0 +/- 1.9 Ma (5.0 m.y., Berriasian/Valanginian is 137.0 +/- 2.2 Ma (7.2 m.y.), Tithonian/Berriasian (Jurassic/Cretaceous) is 144.2 +/- 2.6 Ma (6.5 m.y.), Kimmeridgian/Tithonian is 150.7 +/- 3.0 Ma (3.4 m.y.), Oxfordian/Kimmeridgian is 154.1 +/- 3.2 Ma (5.3 m.y.), Callovian/Oxfordian is 159.4 +/- 3.6 Ma (5.0 m.y.), Bathonian/Callovian is 164.4 +/- 3.8 Ma (4.8 m.y.), Bajocian/Bathonian is 169.2 +/- 4.0 Ma (7.3 m.y.), Aalenian/Bajocian is 176.5 +/- 4.0 Ma (3.6 m.y.), Toarcian/Aalenian is 180.1 +/- 4.0 Ma (9.5 m.y.), Sinemurian/Pliensbachian is 195.3 +/- 3.9 Ma (6.6 m.y.), Hettangian/Sinemurian is 201.9 +/- 3.9 Ma (3.8 m.y.), Rhaetian/Hettangian (Triassic/Jurassic) is 205.7 +/- 4.0 Ma (3.9 m.y.), Norian/Rhaetian is 209.6 +/- 4.1 Ma (11.1 m.y.), Carnian/Norian is 220.7 +/- 4.4 Ma (6.7 m.y.), Ladinian/Carnian is 227.4 +/- 4.5 Ma (6.9 m.y.), Anisian/Ladinian is 234.3 +/- 4.6 Ma (7.4 m.y.), Olenekian/Anisian is 241.7 +/- 4.7 Ma (3.1 m.y.), Induan/Olenekian is 244.8 +/- 4.8 Ma (3.4 m.y.), Tatarian/Induan (Permian/Triassic) is 248.2 +/- 4.8 Ma. The uncertainty in the relative duration of each individual stage is much less than the uncertainties on the ages of the stage boundaries.
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Benthic foraminiferal δ¹⁸O records place limits on the history of glaciation, suggesting the presence of ice sheets at least intermittently since the earliest Oligocene. The best indicator of ice growth is a coeval increase in global benthic and western equatorial planktonic δ¹⁸O records. Although planktonic isotope records from the western equatorial regions are limited, subtropical planktonic foraminifera may also record such ice volume changes. It is difficult to apply these established principles to the Cenozoic δ¹⁸O record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events. The authors improved Oligocene to Miocene correlations of δ¹⁸O records and erected eight oxygen isotope zones (Oi1-Oi2, Mi1-Mi6). Benthic foraminiferal δ¹⁸O increases which can be linked with δ¹⁸O increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near Antarctica. These new correlations of middle Miocene benthic and western equatorial planktonic δ¹⁸O records show remarkable agreement in timing and amplitude. They interpret benthic-planktonic covariance to reflect substantial ice volume increases near the bases of Zones Mi2 (circa 16.1 Ma), Mi3 (circa 13.6 Ma), and possibly Mi5 (circa 11.3 Ma). Possible glacioeustatic lowerings are associated with the δ¹⁸O increases which culminated with the bases of Zone Mi4 (circa 12.6 Ma) and Mi6 (circa 9.6 Ma), although low-latitude planktonic δ¹⁸O records are required to test this. These inferred glacioeustatic lowerings can be linked to seismic and rock disconformities.
We developed a Late Cretaceous sealevel estimate from Upper Cretaceous sequences at Bass River and Ancora, New Jersey (ODP [Ocean Drilling Program] Leg 174AX). We dated 11-14 sequences by integrating Sr isotope and biostratigraphy (age resolution +/-0.5 m.y.) and then estimated paleoenvironmental changes within the sequences from lithofacies and biofacies analyses. Sequences generally shallow upsection from middle-neritic to inner-neritic paleodepths, as shown by the transition from thin basal glauconite shelf sands (transgressive systems tracts [TST]), to medial-prodelta silty clays (highstand systems tracts [HST]), and finally to upper-delta-front quartz sands (HST). Sea-level estimates obtained by backstripping (accounting for paleodepth variations, sediment loading, compaction, and basin subsidence) indicate that large (>25 m) and rapid (much less than1 m.y.) sea-level variations occurred during the Late Cretaceous greenhouse world. The fact that the timing of Upper Cretaceous sequence boundaries in New Jersey is similar to the sea-level lowering records of Exxon Production Research Company (EPR), northwest European sections, and Russian platform outcrops points to a global cause. Because backstripping, seismicity, seismic stratigraphic data, and sediment-distribution patterns all indicate minimal tectonic effects on the New Jersey Coastal Plain, we interpret that we have isolated a eustatic signature. The only known mechanism that can explain such global changes-glacio-eustasy-is consistent with foraminiferal delta(18)O data. Either continental ice sheets paced sea-level changes during the Late Cretaceous, or our understanding of causal mechanisms for global sea-level change is fundamentally flawed. Comparison of our eustatic history with published ice-sheet models and Milankovitch predictions suggests that small (5-10 x 10(6) km(3)), ephemeral, and areally restricted Antarctic ice sheets paced the Late Cretaceous global sea-level change. New Jersey and Russian eustatic estimates are typically one-half of the EPR amplitudes, though this difference varies through time, yielding markedly different eustatic curves. We conclude that New Jersey provides the best available estimate for Late Cretaceous sea-level variations.
Net relative vertical movements of continental surfaces can be identified and compared on an intercontinental scale by calculating percentages of flooding on continents at specific time intervals in the geologic past and then plotting the percentages on the corresponding hypsometric curves. Once a sea level curve is determined, the effects of sea level change can be subtracted from the elevation of the points on the curves, thereby giving the actual directions of net movements relative to sea level. Substantial net uplifts relative to other continents are indicated for Europe and Australia between the Albian and Turonian, for North America in the Cenozoic and for Africa between the Eocene and present. Narrower estimates of the time of uplift are not yet possible because the hypsometric curves are highly generalized and the paleogeographic data contain an unknown amount of error.Estimates of sea level changes suggest a late Cretaceous sea level elevation of about 200 m above present sea level. If correct, all areas that were covered by the late Cretaceous sea and that now lie above 200 m have been uplifted since the Cretaceous. The largest areas of uplift are in the Western Interior of North America and in northern and northeastern Africa, suggesting that uplift of these areas could account for the large net uplift during the Cenozoic in these two continents. The uplift in northern and northeastern Africa appears to be related, in part, to plateau uplifts and rifting. The origin of uplift in the Western Interior is less clear but may be an isostatic adjustment following late Cretaceous to early Tertiary driving subsidence and sediment loading in the Western Interior foreland basin.
Three million years ago, prior to the onset of northern hemisphere glaciation, global mean temperatures may have been as much as 3.5 °C warmer than at present. We present evidence, based on the carbon isotopic composition of marine organic matter, that atmospheric CO2 levels at this time were on average only about 35% higher than the preindustrial value of 280 ppm. We also present carbon isotopic evidence for stronger thermohaline circulation in the Atlantic Ocean during the warmest intervals and propose that the North Atlantic “conveyor belt” may act as a positive feedback to global warming by enhancing sea ice retreat and decreasing high latitude albedo. Based on our results, it seems unlikely that the mid Pliocene warm period was a doubled CO2 world.